Method of forming a die

ABSTRACT

A method for forming a die, including forming a pre-formed mold by providing a preliminary layer on a substrate and performing a micro-machining process on the preliminary layer. Due to the micro-machining process, the method can fabricate a pre-formed mold with high precision for forming a mold. The die is fabricated by the mold for performing a molding process to obtain a workpiece with a predetermined shape.

BACKGROUND

The invention relates in general to a method of forming a die to obtaina workpiece with high precision.

Conventional molding processes are widely used in shaping workpieces. Amold is fabricated in which the profile of the mold is opposite to thatof workpiece. The mold then presses the workpiece which is completeafter removal from the die.

A conventional molding process is shown in FIG. 1. A mold material 10 isprovided to form a mold 11 by performing a normal machining process. Themachining process can include conventional methods such as drilling,milling, turning, or grinding, to manufacture the mold 11 which has aprofile opposite to that of the workpiece. Next, the mold 11 is fixed ona die base 12 to form a die 1. The workpiece 2 is then pressed by thedie 1. After removal from the die 1, the workpiece 2 has a predeterminedshape.

The mentioned process has many advantages including rapid manufacturingproducts time, enabling mass production. Recently, elements required inmechanisms and apparatuses, however, with small size cannot be satisfiedby the conventional methods because the mold is too small to be shapedthereby. The conventional methods such as drilling, milling, turning, orgrinding and the machines corresponding thereto, such as drillingmachine, milling machine, turning machine, or grinding machine, arerestricted in precision accuracy. Generally, machining precision of theconventional skills is above 1 mm. In some machine tools for drilling,milling, turning, or grinding, precision of machining can be furtherenhanced. Due to the existed limitations, however, that workpiecesmanufactured by conventional methods do not conform to the desiredprecision.

SUMMARY

The invention provides methods of forming a die to obtain workpieceswith high precision, satisfying the requirement of small sizeworkpieces.

A method of forming a die for performing a molding process to obtain aworkpiece with a predetermined shape, the method comprises providing asubstrate; forming a pre-formed mold by providing a preliminary layer onthe substrate and performing a micro-machining process on thepreliminary layer; providing a mold material on the pre-formed mold toform a mold; and fabricating the die with the mold.

In an exemplary embodiment, the preliminary layer comprisesphoto-sensitive material and the micro-machining process compriseslithographic process, comprising providing a photo mask above thepreliminary layer to form a masked module; exposing the masked module toradiation, wherein a portion of the preliminary layer is exposed to theradiation; and developing the preliminary layer to form the pre-formedmold. In the above mentioned method, the portion of the preliminarylayer exposed to radiation or a portion of the preliminary layerunexposed to radiation is removed in the developing step.

In an exemplary embodiment, the micro-machining process comprisesprecision electrical discharge machining, laser machining or rapidprototyping machining.

In an exemplary embodiment, the rapid prototyping machining is selectedfrom a group consisting of stereo lithography (SL), selected lasersintering (SLS), laser engineering net shaping, three dimensionalprinting (3DP), fused deposition modeling (FDM), laminated objectmanufacturing (LOM) and inkjet forming method.

In an exemplary embodiment, the mold material is provided on thepre-formed mold by electroforming or powder metallurgy forming.

In an exemplary embodiment, the molding process is selected from a groupconsisting of pressing, extruding, die casting, forging, rolling andinjection molding.

In an exemplary embodiment, the mold material is nickel-based alloy orchromium-based alloy, selected from a group consisting of nickel cobalt,nickel phosphide, nickel cobalt phosphide, nickel tungsten, nickelrhenium, nickel palladium, nickel chromium, nickel carborundumphosphide, nickel graphite, and nickel manganese.

In an exemplary embodiment, Vickers Hardness Number of the mold isgreater than 450HV and precision accuracy of the mold is less than 1 mm.

In an exemplary embodiment, further comprises performing a durationenhancing process on the mold or the die. The duration enhancing processis selected from a group consisting of heat treatment, surface coating,air cooling, and fluid cooling process.

In an exemplary embodiment, the surface coating process comprisescoating a protection film on the die with a thickness of 1 to 8 um, theprotection film is selected from a group consisting of aluminum nitride,aluminum titanium nitride, chromium nitride, aluminum carbide anddiamond-like carbon (DLC).

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional method of forming a die;

FIG. 2 is a schematic diagram of a method of forming a die according tothe invention;

FIG. 3 is a schematic diagram of a lithographic process; and

FIG. 4 is a schematic diagram of another method of forming a dieaccording to the invention;

DETAILED DESCRIPTION

An exemplary embodiment is shown in FIG. 2. In a method for forming adie of the invention, a substrate 35 is provided. The substrate 35 is abase for forming a pre-formed mold 36 with a micro-machining process.Preferably, the micro-machining process includes a lithographic process,precision electrical discharge machining or a laser machining. For aconvenient and simple description, the lithographic process is givenbelow as an example.

Referring to FIG. 3, a pre-formed mold 36 is formed by providing apreliminary layer 34 on the substrate 35. Preferably, the preliminarylayer 34 is formed by deposition in a semiconductor process, but is notlimited thereto. The preliminary layer 34 is made by a photo-sensitivematerial. A photo mask 37 is provided above the preliminary layer 34. Apattern on the photo mask 37 corresponds to the required pre-formed mold36. A radiation 38 is provided on the photo mask 37. The pattern on thephoto mask 37 allows parts of radiation 38 to pass through and furtherexpose the preliminary layer 34. Preferably, the portion of the photomask 37 allowing radiation 38 to pass through has the same profile asthe required pre-formed mold 36, and vice versa, as long as thedeveloper can be matched in the subsequent developing step. Thedeveloping step is then preformed in which a developer is used to removethe portion of the preliminary layer 34 exposed by radiation 38 (or theportion of the preliminary layer 34 unexposed to radiation 38), so thatthe preliminary layer 34 is formed to a pre-formed mold 36.

The lithographic process mentioned can manufacture a pre-formed mold 36with high precision. Generally, the lithographic process is widely usedin a semiconductor process to easily manufacture the pre-formed mold 36with precision accuracy of less than 1 mm. Otherwise, the pre-formedmold 36 may be manufactured by precision electrical discharge machining,laser machining or rapid prototyping machining. The precision electricaldischarge machining comprises providing a pre-formed mold material (notshown) in an electrical discharge machine to operate, such that apre-formed mold 36 with precision accuracy of less than 1 mm isachieved. In the precision electrical discharge machining, however, thepre-formed mold material is limited to metal. The laser machiningcomprises providing a pre-formed mold material in a laser machine andrequires a high energy laser to operate, such that a pre-formed mold 36with precision accuracy of less than 1 mm is also achieved. In the lasermachining, the type of the pre-formed mold material is not limited.Further, the rapid prototyping machining mentioned is selected from agroup consisting of stereo lithography (SL) , selected laser sintering(SLS), laser engineering net shaping, three dimensional printing (3DP),fused deposition modeling (FDM), laminated object manufacturing (LOM)and inkjet forming method, achieving a pre-formed mold 36 with precisionaccuracy less than 1 mm.

Referring back to FIG. 2, after the pre-formed mold 36 is performed, amold material (not shown) is provided on the pre-formed mold 36 to forma mold 31. As mentioned, the mold material may be provided on thepre-formed mold 36 by electroforming. The substrate 35 and thepre-formed mold 36 are placed in an electroforming machine, and the moldmaterial is gradually filled on the pre-formed mold 36, forming the mold31. Otherwise, the mold material may be provided on the pre-formed mold36 by powder metallurgy forming. The substrate 35 and the pre-formedmold 36 are placed in a powder metallurgy forming machine, the powder ofmold material is filled, and the processes of compression and sinteringis performed, forming the mold 31.

Sequentially, a die 3 is fabricated by assembling the mold 31 and a diebase 32. The die 3 can perform a molding process to obtain a workpiece4. Preferably, the molding process is a pressing process. Namely, thedie 3 is fixed on a pressing machine, so that the die 3 presses theworkpiece 4 with the predetermined shape. The molding process is notlimited to the above, an extruding, die casting, forging, rolling andinjection molding process can also achieve the same result. The materialof the mold 31 may be nickel-based alloy or chromium-based alloy,selected from a group consisting of nickel cobalt, nickel phosphide,nickel cobalt phosphide, nickel tungsten, nickel rhenium, nickelpalladium, nickel chromium, nickel carborundum phosphide, nickelgraphite, and nickel manganese, and Vickers Hardness Number of the moldis greater than 450HV, for forming a more durable mold 31. After themold 31 is formed, a duration enhancing process such as heat treatment,surface coating, air cooling, or fluid cooling process is performed onthe mold 31 or the die 3, so that the structure of the mold 31 isenhanced to facilitate the molding process. That is, the durationenhancing process can raise the reliability of the mold. The surfacecoating process mentioned comprises a protection film coated on the die3 or the mold 31. The protection film is selected from a groupconsisting of aluminum nitride, aluminum titanium nitride, chromiumnitride, aluminum carbide and diamond-like carbon (DLC), with athickness of 1 to 8 um, to enhance the structure of the mold 31. Theduration enhancing process is important to the die 3, and especially tothe workpiece 4 with precision less than 1 mm. The mold 31 may be brokenduring the molding process if the strength of the mold 31 is adequatedue to the small size. Preferably, the material of the workpiece 4 isselected from copper, copper alloy, aluminum, aluminum alloy, nonmetaland a combination thereof, not limited thereto.

Another exemplary embodiment is shown in FIG. 4. The embodiment issimilar to that previously described. The different is that only theprotrusion of the mold 31 is formed during fabricating the mold 31. Asthe mold 31 is connected to the substrate 35, the mold 31 and thesubstrate 35 is assembled with the die base 32 to form the die 3. Thedie 3 then performs a molding process to obtain a workpiece 4. In thisembodiment, the effect same as the mentioned embodiment is achieved andfurther reduces the numbers of the steps in method and costs associatedwith forming the mold 31 with the mold material.

As mentioned above, the invention increases the precision of the mold toobtain a workpiece with high precision, satisfying the requirements ofsmall size products. The pre-formed mold is formed by a micro-machiningprocess. Due to the micro-machining process, the machining precision isenhanced. The method can achieve the object of obtaining a manufacturedworkpiece with high precision.

While the invention has been described by way of example and in terms ofpreferred embodiments, it is to be understood that the invention is notlimited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements as would be apparent to thoseskilled in the art. Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

1. A method of forming a die for performing a molding process to obtaina workpiece with a predetermined shape, the method comprising: providinga substrate; forming a pre-formed mold by providing a preliminary layeron the substrate and performing a micro-machining process on thepreliminary layer; providing a mold material on the pre-formed mold toform a mold; and fabricating the die with the mold.
 2. The method asclaimed in claim 1, wherein the preliminary layer comprises aphoto-sensitive material and the micro-machining process comprises alithographic process, comprising: providing a photo mask above thepreliminary layer; providing a radiation on the photo mask, wherein aportion of the preliminary layer is exposed by the radiation; anddeveloping the preliminary layer to form the pre-formed mold.
 3. Themethod as claimed in claim 2, wherein the portion of the preliminarylayer exposed to the radiation is removed in the developing step.
 4. Themethod as claimed in claim 2, wherein a portion of the preliminary layerunexposed to the radiation is removed in the developing step.
 5. Themethod as claimed in claim 1, wherein the mold material is provided onthe pre-formed mold by electroforming.
 6. The method as claimed in claim1, wherein the mold material is provided on the pre-formed mold bypowder metallurgy forming.
 7. The method as claimed in claim 1, whereinthe die is fabricated by assembling the mold with a die base.
 8. Themethod as claimed in claim 1, wherein the die is fabricated byassembling the mold and the substrate with a die base.
 9. The method asclaimed in claim 1, wherein the molding process is selected from a groupconsisting of pressing, extruding, die casting, forging, rolling andinjection molding.
 10. The method as claimed in claim 1, wherein themold material is selected from a group consisting of nickel cobalt,nickel phosphide, nickel cobalt phosphide, nickel tungsten, nickelrhenium, nickel palladium, nickel chromium, nickel carborundumphosphide, nickel graphite, and nickel manganese. nickel-based alloy andchromium-based alloy.
 11. The method as claimed in claim 10, whereinVickers Hardness Number of the mold is greater than 450HV.
 12. Themethod as claimed in claim 10, wherein precision accuracy of the mold isless than 1 mm.
 13. The method as claimed in claim 1, further comprisingperforming a duration enhancing process on the mold or the die.
 14. Themethod as claimed in claim 13, wherein the duration enhancing process isselected from a group consisting of heat treatment, surface coating, aircooling, and fluid cooling process.
 15. The method as claimed in claim14, wherein the surface coating process comprises coating a protectionfilm on the die with a thickness of 1 to 8 um, the protection film isselected from a group consisting of aluminum nitride, aluminum titaniumnitride, chromium nitride, aluminum carbide and diamond-like carbon(DLC).
 16. The method as claimed in claim 1, wherein the material of theworkpiece is selected from copper, copper alloy, aluminum, aluminumalloy and nonmetal and a combination thereof.
 17. The method as claimedin claim 1, wherein the micro-machining process comprises precisionelectrical discharge machining.
 18. The method as claimed in claim 17,wherein a pre-formed mold material for the pre-formed mold is providedin an electrical discharge machining center to perform precisionelectrical discharge machining.
 19. The method as claimed in claim 1,wherein the micro-machining process comprises laser machining.
 20. Themethod as claimed in claim 19, wherein a pre-formed mold material forthe pre-formed mold is provided in a laser machining machine to performlaser machining.
 21. The method as claimed in claim 1, wherein themicro-machining process comprises rapid prototyping machining.
 22. Themethod as claimed in claim 21, wherein the rapid prototyping machiningis selected from a group consisting of stereo lithography (SL), selectedlaser sintering (SLS), laser engineering net shaping, three dimensionalprinting (3DP), fused deposition modeling (FDM), laminated objectmanufacturing (LOM) and inkjet forming method.